3:00 p.m., Friday (October 17, 2003)
Math Annex 1100
Groups describe symmetries of single objects. The symmetries of
families of objects are described by groupoids. If we want to study
all families of a certain type of geometric object (Euclidean
triangles, say, or Riemann surfaces), we are led to the notion of
stack. In this talk I will explain what a stack is and why stacks
are useful. I will give a few simple examples. In recent years,
algebraic stacks have become an indispensable tool in algebraic
geometry, but other areas of geometry should profit from
considering stacks, too.
Refreshments will be served at 2:45 p.m. in the Faculty Lounge,
Math Annex (Room 1115).